SHEEP DISEASES : CAUSES, NATURE AND PREVENTION. 311 
causes to the development of disease, and one of the most important 
of these is the management of the land and of feeding. Seeing 
that the growth of animals and vegetables moves in a circle, and 
that both derive their nourishment primarily from the earth, it 
follows that the earth must contain, in order for their vigorous 
growth, all the elements they require and that those elements 
must bear, as I have already remarked in reference to the blood, 
a certain definite proportion to each other. 
Now it is quite clear that if the stockowner year by year takes 
from the land the important constituents of all organic growth by 
putting animals thereon and allowing them to devour the vegetable 
products and then devouring the animals himself or selling them 
to someone else to devour, the land must ultimately become im¬ 
poverished : he cannot eat his cake and have it too. 
It may be held that much of the material taken from the land 
is returned again to it in the shape of urine and dung, but, allow¬ 
ing that this is so, what about the yearly deficit produced by the 
removal of immense quantities of material in the shape of mutton, 
blood, horn, skin, w’ool, <fcc. ? Then it may be said that the air 
and the rain supply vegetables with nitrogen and carbon. Granted, 
again, that this is so, what proportion of soluble matter, especially 
on hillsides, is washed out of the soil by rain ? 
The heather may be burned, but by doing so much of its 
nutrient matter is dissipated in the form of gas, which is largely 
carried away by the wind and benefits the neighboring fields; or, 
if in close proximity to the sea, the fishes mayhap. Certainly the 
ash of the heather contains a small quantity of potash and other 
salts which are thus restored to the grass; that is all, however— 
no nitrogen, no carbon. It would, 1 know, be simply absurd on 
my part to tell the stockowner, as I have heard of some people 
doing, to restore to his hill pastures, in the form of manures, that 
which he annually takes out of them. As a rule he has not the 
means to do so, and if he had, the task of manuring a thous¬ 
and acres of hill would be a Herculean one indeed ; but the farmer 
may give the poor impoverished land, or the best patches of it, 
something in the shape of lime to supply materials for the bones 
of the animals grazing on it, and salt to supply soda to the serum 
